Huntington\'s disease is a rare dominant mutation (H > h), autosomal, and lethal

Question

Huntington's disease is a rare dominant mutation (H > h), autosomal, and lethal in homozygous condition by age 40-50. A heterozygous father (Hh) died from Huntington's disease. What is the chance his son will develop Huntington's disease? (the mother has genotype hh) (a) 100 % (b) 75 % (c) 50 % (d) 25 % Sickle-cell anemia is an autosomal recessive mutation in a gene coding for beta-globin. What is the chance for a healthy child to be born if each of the parents is heterozygous? (a) 100% (b) 75 % (c) 50% (d) 25 % (e) 0% What is the chance for a HEALTHY child to be born if BOTH parents are heterozygous by BOTH of sickle-cell and cystic fibrosis genes? (a) 3/16 (b) 3/4 (c) 1/2 (d) 9/16 (e) 1/16

Explanation / Answer

29. There is a chance of 25% for a healthy child to be born.

Those people affected with sickle-cell trait are also known as carriers. If two carriers have a child, there is a 25% chance their child will have SCA, a 50% chance their child will be a carrier, and a 25% chance that the child will neither have SCA nor be a carrier.

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